Medicine is a science of uncertainty and an art of probability

Dr Stephen Granier, Whiteladies Medical Group, Bristol.

“Medicine is a science of uncertainty and an art of probability”1 William Osler’s statement is no less relevant today. We are confronted by illnesses daily where we need to decide whether the body needs help or if it should be left alone.2 We use our clinical knowledge and skills, and clinical tools and guidelines together with patients’ preferences, to decide whether they need urgent admission, medical intervention or reassurance and advice about self-management and advice about managing uncertainty.

For centuries, medical practice was guided by what charismatic clinicians considered best practice based on “scraps of evidence, anecdotes, bias, preconceived notions and a lot of psychological traps.”3 The first published randomised controlled trial of streptomycin for pulmonary tuberculosis in 19484 set a new standard for clinical research, however, medical practice continued to be largely eminence based practice.

Not long after the term was coined by Guyatt (1991),5 evidence based medicine (EBM) was criticised by eminence based medical practitioners, and the Lancet, for being a “dangerous innovation”, cook book medicine promoted by arrogant managers to cut costs and restrict clinical freedom.6,7 The medical community expressed concerns that non-clinicians and statisticians had no valid contribution to make to medical practice and expressed hostility towards the scientific method of testing a potentially falsifiable hypothesis.

 quarter of a century on, EBM is thriving and the Cochrane Database of Systematic Reviews is one of the “go to” sources for advice on how to care for our patients; its collections of systematic reviews and meta-analyses providing the evidence underpinning many guidelines and much clinical practice. Today, taking the best evidence into practice is what presents an ongoing challenge.

Antibiotics are one of the casualties in this lack of careful gathering and application of evidence. The utility of antibiotics for specific high risk infections coupled with mass production led to indication creep - the widening of indications for their use, often not support by clinical evidence.

Acute respiratory infections are the most common reasons for antibiotic use in adults,8 but how useful are they? Table 1 shows the average benefit of antibiotics compared to the durations of common acute respiratory infections.9-12 On average, they reduce the duration of the main symptoms or days feeling ill by between 8 and 24 hours, a trivial amount in the context of the overall duration. The numbers needed to treat for one additional patient to benefit are between 6 and 22 compared to numbers needed to harm of 8 to 24. So for many patients we may even do more harm than good by prescribing antibiotics and a prescription strengthens the belief that a consultation and antibiotics may be needed in future.13


Table 1. Evidence on the benefit and harms of antibiotics for common acute respiratory infections.9-12


There are some patient groups that may benefit from antibiotic therapy, for example, children under the age of two with bilateral otitis media, those with otorrhoea or patients over 80 years of age with one or more risk factors of hospitalisation in the past year, oral steroids, diabetes or CCF or those over 65 years of age with 2 or more of these risk factors.14

Still there are gaps in our knowledge and needs. Public Health England (PHE), in collaboration with the RCGP, would like to invite you take part in a survey (click here) to identify which conditions you would like to see more evidence for management in your daily clinical practice. The survey takes 7 minutes to complete and your response will be used to determine where research is needed to inform guidance development. On completion, you will have the opportunity to enter your details into a draw to win one of four sets of £50 John Lewis vouchers.


  1. Osler W, Silverman ME, Murray TJ, et al. The Quotable Osler. Philadelphia: American College of Physicians--American Society of Internal Medicine; 2003.

  2. Margaret McCartney. We don’t need nannying for colds. BMJ 2017; 356 doi:

  3. Prasad V & Cifu A. Ending Medical Reversal. Improving outcomes, saving lives. 2015 Johns Hopkins University Press. Baltimore.

  4. Medical Research Council Investigation. Streptomycin Treatment of Pulmonary Tuberculosis. BMJ 1948:2;769-782.

  5. Sacket D, Rosenberg W, Muir Gray J, et al. Evidence based medicine: what it is and what it isn’t. BMJ 1996; 312:71-72.

  6. Evidence-based medicine, in its place. The Lancet 1995;346:785.

  7. Graham-Smith D. Evidence based medicine: Socratic dissent. BMJ 1995;310:1126

  8. Harris A, Hicks, L, Qaseem A. Appropriate antibiotic use for acute respiratory tract infection in adults:  advice for high-value care from the American College of Physicians and Centers for Disease Control and Prevention. Annals Internal Medicine 2016164:425-435.

  9. Venekamp RP, Sanders SL, Glasziou PP, Del Mar CB, Rovers MM. Antibiotics for acute otitis media in children. Cochrane Database of Systematic Reviews 2015, Issue 6. Art. No.: CD000219. DOI: 10.1002/14651858.CD000219.pub4

  10. Spinks A et al. (2013) Antibiotics for sore throat. Cochrane Database of Systematic Reviews 2013, Issue 11. Art.No: CD000023

  11. Lemiengre M, van Driel M, Merenstein D et al. (2012) Antibiotics for clinically diagnosed acute rhinosinusitis in adults. Cochrane Database of Systematic Reviews 2012, Issue 10. Art. No.: CD006089

  12. Smith S, Fahey T, Smucny J, Becker L . Antibiotic treatment of people with clinical diagnosis of acute bronchitis. Cochrane Database of Systematic Reviews 2014, Issue 3. Art. No.: CD000245

  13. Little P, Gould C, Williamson I, et al. Reattendance and complications in a randomised trial of prescribing strategies for sore throat: the medicalising effect of prescribing antibiotics. BMJ. 1997 Aug 9;315(7104):350-2.

  14. Management of infection guidance for primary care for consultation and local adaptation. Public Health England. 2017 London.

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